Aqueous acidic plating baths for electrolytic deposition of copper are used for manufacturing printed circuit boards and IC substrates where fine structures like trenches, through holes (TH), blind micro vias (BMV) and pillar bumps need to be filled or build up with copper. Another application of such electrolytic deposition of copper is filling of recessed structures such as through silicon vias (TSV) and dual damascene plating or forming redistribution layers (RDL) and pillar bumps in and on semiconducting substrates. Still another application which is becoming more demanding is filling through glass vias, i.e. holes and related recessed structures in glass substrates with copper or copper alloys by electroplating.
Conventionally, a combination of various additives is used in aqueous plating bath compositions. For example, electrolytic copper plating baths comprise a multitude of individual additives including levellers, carrier-suppressors and accelerator-brighteners. Similarly, zinc plating baths contain additives to improve inter alia the visual properties of zinc deposits.
The patent application EP 1 069 211 A2 discloses aqueous acidic copper electroplating baths comprising a source of copper ions, an acid, a carrier additive, a brightener additive and a leveller additive which can be poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea (CAS-No. 68555-36-2) which contains an organo-bound halide atom (e.g., covalent C—Cl bonds) in at least one terminus.
US 2009/0205969 A1 describes cross-linked polymers made from urea, N,N-dialkylaminoalkylamine and N,N-bis-(aminoalkyl)-alkylamine as additive for electrolytic metal deposition. The process disclosed therein relates to electrolytic zinc deposition.
Similar urea-based polymers are also reported in U.S. Pat. No. 4,157,388 wherein all urea moieties are bridged via nitrogen containing alkylenes, i.e. secondary, tertiary amines and the like. Cationic derivatives and their use in electrolytic plating bath are disclosed in the German patent application DE 10 2005 060 030 A1. The individual urea moieties in these polymers are linked by quaternary ammonium derivatives.
Ureyl polymers are known in the art from EP 2 735 627 A1 as leveller for the electrolytic deposition of copper. Such polymers are can be obtained by a polyaddition of aminourea derivatives and nucleophiles. WO 2011/029781 teaches the same polymers for the electrolytic deposition of zinc. The latter document also teaches bisurea derivatives of a general formula without disclosing any specific examples. Moreover, the examples relating to said structures are diam ides (examples 5 and 18 therein).
However, such additives when used in acidic copper plating baths are not suitable to fulfil the current and future requirements in manufacture of advanced printed circuit boards, IC substrates and metallisation of semiconducting and glass substrates. Depending on the circuitry layout, BMVs' in printed circuit boards and IC substrates need to be filled with copper not only conformally but completely. Typical requirements for BMV filling are for example: obtaining a completely filled BMV while depositing no more than 12 to 18 μm of copper onto the neighbouring planar substrate areas and at the same time creating a dimple on the outer surface of the filled BMV of no more than 5 μm.
In metallisation of semiconducting wafers, TSV filling must lead to a complete and void-free filling with copper while creating no more than ⅕ of via diameter of overplated copper onto the neighbouring planar areas. Similar requirements are demanded for filling through glass vias with copper.